Messenger RNA therapy (MRT) is becoming an increasingly important approach for the treatment of a variety of diseases. MRT involves administration of messenger RNA (mRNA) into a patient in need of the therapy for production of the protein encoded by the mRNA within the patient body. Lipid nanoparticles are commonly used to encapsulate mRNA for efficient in vivo delivery of mRNA. However, current methods for producing mRNA-loaded lipid nanoparticles suffer poor encapsulation efficiency, low mRNA recovery and/or heterogeneous particle sizes.